4 PLANT-LIFE 



concomitation of substance and circumstance, living 

 matter, presumably protoplasm, became evolved. He 

 suggested that ancient conditions for the appearing of 

 protoplasm were no more favourable than those which 

 are at present in existence, and he was not sure but 

 that its evolution might not still be taking place. These 

 suggestions seem reasonable, and are the articulate 

 expression of a feeling which must exist with many who 

 are exercised about the origins of things. What has 

 happened may surely happen again when the conditions 

 are favourable. It seems more reasonable to think that 

 protoplasm is still being evolved rather than that all 

 that which now is has been derived from a modicum 

 which evolved aeons ago. 



Our speculations are attractive, but we must come 

 down to facts. The fundamental fact in plant and 

 animal life is protoplasm, and a further fact is that it 

 has been differentiated, from a period most remote, 

 into plant and animal forms. Into the mysterious 

 forces which led to such differentiation we shall not 

 venture to inquire; we shall simply take facts as we find 

 them. And one outstanding fact in relation to the 

 simplest life-forms is the difficulty of deciding which is 

 plant and which is animal. The old idea that plants are 

 stationary and animals move does not hold good as a 

 means of distinguishing between the two great king- 

 doms of nature; for there are undoubted plants which 

 swim actively, and the living protoplasts in a tree as 

 stationary as an oak certainly move within the narrow 

 confines of their cell walls. Moreover, there are animals 

 which are sedentary — for example, the sponges, which 



